A variety of athletic endeavors require shoes which firmly support a user's foot and/or ankle. Flexion of the ankle joint may be required to be inhibited in certain directions while permitted in other directions, with the particular support requirements varying depending on the sport. For example, in in-line skating, it is desirable to permit the ankle to flex fore and aft during usage, while it is also desirable to inhibit lateral, or side to side, flexion so that the skate remains properly positioned relative to the user's leg and the ground during skating. In-line skates typically incorporate a shoe having an upper secured to a frame which carries a plurality of wheels along a common longitudinal axis. For maximum control and efficiency of force transfer, it is desirable to maintain the skate wheels and upper in a substantially vertical position, i.e., perpendicular to the plane of the ground. In-line roller skating is generally considered to require higher levels of skill, coordination and strength than conventional paired-wheel roller skating because of the narrow lateral support base associated with in-line roller skate wheels. While balancing in the forward and rearward direction is relatively easy, balancing in the sideward or lateral direction is difficult due to the narrow support base. Thus, proper ankle and foot support within the upper shoe portion of the skate is important. Support considerations for ice skates are similar to those for in-line skates.
Other athletic shoes have differing requirements. For example, a snowboard boot preferably supports the user's ankle so as to control and limit forward and aft flexion, for proper edge control of the snowboard. However, at least some lateral and medial, or side to side, flexion is desired.
Athletic shoes are thus designed and constructed to attempt to provide the type and degree of support required for a particular sport. This task is complicated, however, by the innate variance in anatomical structure from individual to individual. For example, the location of the malleoli, i.e., the laterally protruding ends of the tibia and fibia at the talocrural (ankle) joint, varies upwardly and downwardly from individual to individual. If an athletic shoe which must support the ankle is designed to closely conform to and support the malleoli of any given "nominal" individual, this same shoe may uncomfortably pressure ankles which are upperly or lowerly displaced from nominal for other individuals. To accommodate this variance, athletic shoes which support the ankle, such as in-line skate shoe uppers, typically provide an enlarged recess around the malleoli that will accommodate normal anatomical variance. However, this requirement necessarily induces a certain degree of undesirable loose fit, or "slop", around the ankle joint, which, while avoiding discomfort, also reduces the degree of support and control. Similar difficulties may arise in attempting to properly support variations in the conformation of individuals' heels, metatarsal head regions, arches, and insteps.
To some degree, adjustment for differing foot volumes and support requirements can be provided by adjustable shoe closures. For example, in-line skate boots typically have one of several different types of construction. The most commonly found construction entails a shoe upper constructed from a rigid plastic boot which is secured to or integrally molded with a frame on the underside. The frame receives the plurality of wheels. The interior of the rigid boot receives a removable foam liner. The rigid boot is secured and adjustably fitted around the liner by compression straps or lacings. The malleoli are accommodated within the ankle portion of the rigid boot by concave recesses formed in the interior of the boot on either side of the ankle. While the boot may be cinched down around the user's ankle and lower leg, the necessary slop built into the malleoli recesses and foam situated therein necessarily permits a certain amount of movement of the ankle joint in order to avoid extreme discomfort. Further, no provision is made for adjustment of the fit of the heel, which may shift laterally within the boot if the fit of the boot to that particular individual is not close. Likewise, no provision is made for adjustment of the fit and support around the metatarsal head region.
Another type of conventional in-line skate construction, disclosed in U.S. Pat. No. 5,437,466 to Meibock, the disclosure of which is hereby expressly incorporated by reference, utilizes a rigid base on the underside of which is secured a frame. The upper shoe portion of the skate is formed from a flexible, breathable material such as leather or fabric, which is internally cushioned with layers of foamed elastomer material. The upper shoe portion is secured to the upper surface of the base. A rigid support structure extends upwardly from the base on the outside of the flexible upper shoe portion. The support structure includes a heel cup and a pivoting ankle cuff. Malleoli recesses are provided within the cuff. The flexible upper shoe portion is closed by lacing and/or compression straps, which provides a better fit than that afforded by the rigid plastic boots of other skates. However, the degree of adjustment for fit and support is still limited to a certain degree.
Another type of in-line skate construction utilizes a flexible upper shoe portion that is again bonded to a rigid base to which a frame is secured for the mounting of wheels. The flexible upper shoe portion is reinforced internally by a heel cup secured to the base, and a pivoting ankle cuff, mounted internally within the exterior fabric of the upper shoe portion. The upper shoe portion is completed by layers of foam padding which are secured within the interior of the internal supporting structure. Such a construction is disclosed in pending U.S. patent application Ser. No. 08/668,278, filed Jun. 12, 1996, the disclosure of which is hereby expressly incorporated by reference. The innermost foam layer is contoured around the malleoli to create malleoli recesses, which are backed by corresponding recesses formed in the internal ankle cuff. This construction again provides considerable improvement over the comfort and fit of rigid-shelled in-line skates. However, a certain degree of looseness is necessarily required around the malleoli and other locations of the shoe.
Attempts have been made in sport shoe construction to incorporate plastic materials, such a putties or gels, into the interior of the shoe, in order to more closely conform to a particular user's anatomical structure and size. Conventional in-line skates have been constructed which contain a putty contained within a pouch on either side of the malleoli. The putty within the pouch is deformed by the malleoli when the upper of the skate is secured around the user's ankle, providing a fit which is customized to a certain extent. However, this construction suffers from the tendency of such putties or other conventional plastic materials to reduce in yield stress (i.e., to thin or become less viscous) when warmed. Thus, when the skate is initially fitted on the user and use begins, the putty is stiff and uncomfortable. The putty gradually warms due to heat transferred from the user's foot and ankle, becoming thinner, more malleable, and providing less support. As the putty is deformed, the skate may become more comfortable; however, the support provided by the warmed putty reduces the degree of support provided, exactly opposite the effect which would be optimum.
Further solutions to the fit problem have been presented by gels developed in recent years which are responsive to temperature. A first type of thermally response gel shrinks in volume by expressing a liquid solute when heated above a threshold temperature. Another type of thermally responsive gel is a reverse thermal gel. The term "reverse thermal gel" refers to a material which undergoes a dramatic increase in viscosity or yield stress as it is warmed from an initial temperature to an elevated temperature. Examples of thermally responsive gels and usages therefor are disclosed in International PCT Application Serial No. WO96/28057, published Sep. 19, 1996 and in International PCT Application Serial No. WO96/28056, published Sep. 19, 1996. These references disclose a variety of types of gels which go through a transition in response to an environmental trigger such as temperature. Conformable structures, including sporting equipment, which incorporate such gels within compliant plastic bladders are also disclosed.
In particular, the '056 PCT Application states that such bladders may be utilized in orthotics, socks, and joint and ankle supports. The bladder may include an internal foam layer, which further stiffens the contained reverse thermal gel after its transition due to the difficulty in flowing the thickened gel through the internal pores of the film. An alternate reverse thermal gel bladder construction including multiple chambers connected by passageways, which further stiffens the bladder because of the resistance to flow of the transitional gel through the narrow passageways, is also disclosed.
The '057 PCT Application further discloses the use of bladders containing reverse thermal gels or gels which express a liquid that are positioned in the heel, in the tongue, in the collar below the malleoli, in the foot bed, and in the metatarsal region of a shoe. Use of such temperature responsive gel filled bladders in a variety of athletic shoes, including skates and skis, and the use for ankle support, is stated generally but without any disclosure of critical features that would make it practicable and effective. The use of bladders including multiple chambers and narrow connecting passageways which contain and further stiffen reverse thermal gels is again suggested.
All of the applications of reverse thermal gel filled bladders disclosed in the two above-identified PCT Applications utilize the bladders to conform to anatomic structure of the user's foot and therefore more closely fit the foot. The reverse thermal gel is always contained within a single or multiple compartment fixed volume bladder. There is no mechanism disclosed for altering the volume of the reverse thermal gel which is incorporated into the bladder chamber or chambers that support the anatomic structure. The construction of a multiple compartment bladder having a first compartment which contains a gel that expresses a liquid into a separate compartment of the bladder upon temperature elevation is disclosed. However, such gels which express liquid upon heating dramatically shrink in volume when this transition occurs, and therefore provide significantly reduced support in the area where the gel is located after transition. Such volume transitioning gels are thus unsuitable in applications where it is desirable to provide an enhanced degree of support from the gel after transition. Further, there is no workable disclosure of how to incorporate any of the thermally responsive gels and bladders disclosed into an athletic shoe for the support of an ankle.